Device for a cyclone scrubber

ABSTRACT

A device for an axial cyclone ( 1 ) of the kind which is used for separating a fluid from a gas, where the gas flowing through the axial cyclone ( 1 ), primarily in the axial direction of the axial cyclone ( 1 ) assigns a rotation around the centre axis ( 12 ) of the axial cyclone ( 1 ), and where the axial cyclone ( 1 ) comprises in the flow direction of the fluid an inlet pipe ( 2 ), a transitional part ( 4 ) and a downstream pipe ( 6 ) where the downstream pipe ( 6 ) is supplied with a cross-sectional area smaller than the cross-sectional area of the inlet pipe.

This invention concerns a cyclone scrubber. More precisely it concerns acyclone of the kind which is used for separating out a fluid, preferablyin the form of droplets, from a gas.

When separating fluid droplets from a gas or a gas mixture, for examplewater droplets from air or condensate from a petroleum gas, the size ofthe smallest droplets to be separated are determining for the efficiencyof the separation process. It is also desirable that the separation iscarried out with as little loss of pressure in the gas flow as possible,in that a pressure loss in a process most often causes a cost of energy.

Scrubbing a gas can advantageously be carried out by passing the gaswhich is to be cleaned, through a cyclone. It has been shown thatso-called axial cyclones, where the gas flowing though a pipe primarilyin the axial direction of the pipe, assigns a rotation around the centreaxis of the pipe, are well suited for this purpose.

Axial cyclones in prior art are usually formed like a cylindrical pipein which a rotational element is concentrically placed, comprising acylindrical, preferably substantially drop-shaped body and several axialvanes distributed around the pipe axis, between the body and theinternal surface of the pipe.

When gas flows in between the vanes, the velocity of flow increases dueto the body's reduction of the cross-sectional area of the pipe, and dueto the vanes the gas assigns a rotation around the axis of the pipe. Therelative to the gas heavier fluid droplets are slung outwards by thecentrifugal force towards the pipe mantel in the pipe downstream of therotational element. The pipe of the cyclone can downstream therotational element be equipped with longitudinal slots through which thefluid droplets can flow out.

The central body of the rotational element causes that the flow velocityof the gas nearest to the body decelerates. In this way, some of thedroplets may be deposited on the body and will, due to low rotationalspeed, not be separated out downstream of the rotational element. Thisphenomenon is often called “fluid creep”.

The common practice in accordance with prior art of placing a centralbody in the rotational element has demonstrated not being able toachieve the necessary degree of separation required for someapplications.

The object of the invention is to overcome the disadvantages in priorart.

The object is achieved according to the invention by the features givenin the description below and the following patent claims.

In accordance with the invention, the flowing gas is assigned thenecessary acceleration by conically reducing the diameter of the cyclonepipe in the section at the rotational element from one diameter upstreamof the inlet of the rotational element to a smaller diameter downstreamof the outlet of the rotational element.

The rotational element according to the invention does not comprise anycentral body, in that the axial vanes distributed around the centre ofthe cyclone pipe join at the inlet of the rotational element. Therotational element itself thus reduces the cyclone's cross-sectionalflow area only to an insignificant extent, and thereby contributesneither to an extent worth mentioning in reducing the flow velocity ofthe gas. In practice, the reduction of area does not exceed 20% of thecross-sectional flow area.

Some of the droplets that exist in the gas meet the conical part of thecyclone when flowing though the rotational element and are already thereseparated out from the fluid. Even if the droplets should remainattached to the conical part, they will, after flowing past therotational element, escape out through the slots in the area downstreamof the. cyclone. Similarly, droplets depositing on the axial vanes willbe pulled into the rotating gas and be slung out through the slots.

The reduction in the pipe diameter downstream of the rotational element,which differs from prior art, causes that gas of equal rotating velocityis given a greater centrifugal force at the internal cylinder surface ofthe cyclone.

Experiments have shown that an axial cyclone according to the inventioncompared with axial cyclones according to prior art, under similarconditions, will demonstrate a considerably improved efficiency.

In the following a description of a non-limiting example of a preferredembodiment is given which is represented in the following drawing,where:

FIG. 1 shows an axial cyclone where a part of the mantel of the cyclonehas been removed to illustrate the rotational element of the cyclone,and where the arrows indicate the is direction of flow through thecyclone.

In the drawings reference number 1 denotes an axial cyclone comprising,in the flow direction of the gas, an inlet pipe 2, a conicaltransitional component 4 and a downstream pipe 6. The downstream pipe 6is supplied with a number of slots 8;

A rotational element 10, which comprises a number of axial vanes 14distributed around the centre axis 12 of the axial cyclone, is placed inthe conical transitional part 4, where the vanes project from asubstantially common joint 16, where the joint 16 at inlet side 10 ofthe rotational element corresponds with the centre axis 12, primarily ina radial direction towards the mantel of the conical transitional part4;

When gas and fluid droplets flow into the inlet pipe 2 and further intothe rotational element 10, see arrows in FIG. 1, the in-flowing fluidassigns a rotation by the axial vanes 14. Simultaneously, the flowvelocity of the fluid increases due to the reduction in cross-sectionalarea in the conical transitional part 4. Primary separation of the fluiddroplets from the gas takes place in the downstream part 6 of the axialcyclone where the rotating movement of the gas around the centre axis 10causes the, as compared with the gas, heavier fluid droplets to be slungout through the slots 8.

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 5. A device foran axial cyclone of the kind which is used for separating a fluid from agas, where the gas during the flow through the axial cyclone, primarilyin the axial direction of the axial cyclone assigns a rotation aroundthe center axis of the axial cyclone and where the axial cyclone in thedirection of flow comprises an inlet pipe, a transitional part with arotational element, and a downstream pipe, the cross-sectional area ofthe downstream pipe is smaller than the cross-sectional area of theinlet pipe, wherein no gap exists between the rotational part.
 6. Thedevice in accordance with claim 1, wherein the rotational element islocated in the transitional part.
 7. The device in accordance with claim1 wherein said rotational element comprises axial vanes, said axialvanes project from a substantially common joint primarily radial outwardin the direction of the internal surface of the axial cyclone.
 8. Thedevice in accordance with claim 1 wherein the cross-sectional area ofthe rotational element in the flow direction is insignificant ascompared with the flow area of the axial cyclone.